Morena Costello of Staten Island is accompanied by Joseph Nicola, the father of her son, outside Brooklyn Federal Court Thursday. Ms. Costello pled guilty to obstructing an investigation of a plot to kill two doctors and two nurses she blamed for her father's death. Jesse Ward for New York Daily News

STATEN ISLAND, N.Y. -- Inconsolable for months over her father's death, Port Richmond resident Morena Costello tried to rub out the two Staten Island University Hospital doctors and two nurses she blamed for his demise.

The macabre episode moved toward a final resolution Thursday when Ms. Costello, 40, admitted to her role in the scheme.

She pleaded guilty in Brooklyn federal court to obstruction of an investigation and faces up to 57 months in prison. A sentencing date has not been set.

"All of us are in agreement that this case was impacted by her mental health," said Ms. Costello's lawyer, Mildred M. Whalen, of Brooklyn, on Friday. "This is a tragedy."

According to court papers, Ms. Costello told the "hit man" she wanted the doctors and nurses "to suffer like her father suffered."

The bizarre chain of events was set in motion in January 2010 when Ms. Costello's father, Bella Costello, 65, also a Port Richmond resident, died of heart failure.

Ms. Costello had cared for her ailing father for a number of years.

She became distraught afterward, and began exhibiting "psychotic symptoms and hallucinatory visions," according to statements made in court shortly after her arrest.

She ultimately hatched the murder scheme.

In late July 2010, Ms. Costello contacted an unidentified source and asked if he could help find a hit man to kill the doctors and nurses she believed responsible for her father's death, said court papers. Those documents did not identify the intended targets.

After several face-to-face and telephone talks, the source told Ms. Costello on Oct. 22, 2010, that someone would contact her. Three days later, the FBI agent telephoned Ms. Costello and arranged an Oct. 28 meeting.

As they sat in the "hit man's" car, Ms. Costello produced a photo of her father and a list with the doctors' and nurses' names. She had also written down the doctors' and nurses' physical descriptions and noted the shift one nurse works and the type of car one doctor drives.

In addition, Ms. Costello brought her father's death certificate to the meeting, said court papers.

When the agent, at one point, asked what she wanted him to do, Ms. Costello allegedly pointed to the word "death" on the certificate and said, "Can you read this part right here?"

Ms. Costello was charged with obstructing an investigation for altering the hand-written list of intended victims, said prosecutors. She also was indicted on charges of murder for hire and obstruction of official proceedings.

She faces 46 to 57 months in prison, said a spokesman for Loretta E. Lynch, U.S. attorney for the Eastern District of New York.

Citing her client's mental health and other factors, Ms. Whalen, the defense lawyer, said she is hopeful of Ms. Costello receiving a significantly shorter sentence.

"I think there are strong arguments to make that her intent was not to commit murder-for-hire," she said.

Arleen Ryback, a University Hospital spokeswoman, said she couldn't comment on the case. But she did say the hospital is grateful the doctors and nurses weren't hurt.